Regulator for calutron ion source



Jan. 3l, 1956 l.. F. WOUTERS 2,733,345

REGULATOR FOR cALUTRoN 10N SOURCE Filed Nov. 28, 1945 2 Sheets-Sheet l INVENTOR. Lou/s E WOUTERS ATTORNEY.

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REGULATOR. FOR CALUTRON ION SOURCE i Filed Nov. 28, 1945 2 Sheets-Sheet 2 O HEATER 619 F/ A MEN 7' s URRL Y 77 ARC SUPPL Y ,So/145,4 R0. M

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2,733,345 REGULATOR FOR CALUTRON ION SOURCE Louis F..Wouter's, Oakland, Calif., assignox" tothe United Statesof America as represented by the United States Atomic Energy Commission Application November 28, 1945, Serial No. 631,416 16 Claims. (Cl. 25o-41.9)

The present invention relates to regulators forelectric discharge devices and more particularly to regulators for calutron ion sources.

It is an object of this. invention to provide a regulator for stabilizing'the operation of a calutron ion generator.

Another object ofA this invention is to provide a regulator for stabilizirigthe operation of a calutron ion gen'- erator ofthe arc discharge type. Y

Still another object of this invention is to provide a regulator for a calutro'n ion generator of the hot cathode arc discharge type which has a highly stable rate of ion production. v.

At the outset it is noted thatacalutron is a machine of the character disclosed in the copending application of Ernest 0,'Lawrence, Serial No. 557,784, filed October 9, l1944, and now Patent No. 2,709,222 granted'May 24, i955, and is employed to separate the constituent isotopes ot an element and more particularly to increase the proportion of a selected isotope in an element containing several isotopes in order to produce the element enriched with the selected isotope. For eirample, themachineis especially useful in producing uranium enriched with Uzas Such a calutron essentially comprises means for vaporizing a quantity ofv material containing an element thatis lto be enriched with a selected one of its several isotopes; means for subjecting the vapor to ionization, whereby at least a portion of the vapor is ionized causing ions of the several isotopes of the element to be produced; electrical means for segregating the ions from-the un-ionized vapor and for accelerating the segregated ions through'relatively high velocities; electromagnetic meansv for deflectingthe ions along curved paths, the radiiof curvaturesrof the paths of the io'ns being proportional to the square roots of the masses of the ions, whereby the ,ions aie concentrated in accordance with their masses; and means for dei'nizing and collectingthe selected ions thus concentrated theie by tok produce a deposit of the element enriched with the selected isotope. Y

The invention', both as to its organization and method of operation together with other objects and advantages thereof, will best be understood by reference to the following-specification taken in connection with the accompanying drawings, in which Figure l is a diagrammatic view of a calutron and the various currentsupplies and arc regulator connected to the ion generatonthe'reof;

Fig. 2 is ardi'agrammatic sectional view of the calutron taken along the line 2 2 of Fig. l;

` Fig. 3 is a diagrammatic view of a calutron ion gen-.-

erator together with the various current supplies associated therewith and a modied form of arc regulator connected thereto; and

Fig. 4 is a diagrammatic` view of acalutron ion generator together with the various current supplies asso`- ciated therewith and another modified fom of arc'regulater connected thereto'. l

Referring now more particularly toA Figs. l and`2'of the drawings, there is illustrated a representative yexample of a calutron 10 of the c aracter noted, that comprises magnetic field structure including upper, and lower pole pieces 11 and 12, provided with substantiallytlatparallel"sp'ac e dapart pole faces, ,and avrtank 13 disposed between the pole facesiof the pole pieces 11 and 12. The

United States Patentl r' ICC 2, pole pieces 11 and 12 carry windings, not shown, which are adapted to be energized in order to produce a substantially uniform and relatively strong magnetic tield therebetween, which magnetic field passes through the tank 13 and the various parts housed therein. The tank 1 3 Vis of tubular configuration, being substantially crescent-shaped in plan, and comprising substantially flat parallel spaced-apart top and bottom walls 14 and 15, upstanding curved inner and outer side walls 16 and 17, and end walls 18 and 1 9. The end walls 18 and 19 close the opposite ends of the tubular tank 13 and are adapted to be removably secured in place, whereby the tank 13 is hermetically sealed. Also, vacuum pumping apparatus, not shown, is associated with the tank 13, whereby the interior of the tank 13 may be evacuated to a pressure of the order of 10-5 to 10?-4 mm. Hg. Preferab1y, the component parts of the tank 13 are formed of steel, theV top and. bottom walls 14and 1 5 thereof being spaced a short distance from the pole faces of the upper and lower pole pieces 11 a nd 12, respectively, the tank 13 being retained in such position in any suitable manner, whereby the top and bottom walls 14 and 15 constitute in effect pole pieces with Vrespect to theinterior of the tank 13, as explained more fully hereinafter.

The removable end wall 18 suitably supports a source unit 20 comprising a charge receptacle 21 and a communicating arc block 22. An electric heater 23 is arranged in 4heat exchange relation Y with the charge receptacle 21v and is adapted to be connected to a suitable source of heater supply, whereby the charge receptacle 21 maybe appropriately heated, the charge receptacle 21 being formed of steel or `the like. The arc block 22 is formed, at least partially, of carbon or graphite and is substantially C-shaped. in plan, an opstanding slot 24 being formed in the Wall thereof remote from the charge receptacle 2 1. Thus, the arc block 22 is of hollow conf struction, the` cavity therein communicating with the interior of the charge receptacle 21.

, Also, the removable end wall 1S cathode 25 adapted to be connected to a suitable source of filament supply, the larnentary cathode 25 overhanging the upper end of the are block 22 and arranged in alignment with respect to the upper end of the cavity formed therein. The arc block22 carries an anode 26 disposed adjacent the lower end thereof and arranged inl alignment with respect to the cavity formed therein. Also, the are block 22 carries a Acollirnating electrode 27 disposedfadjacent the upper end thereof and having an elongated collimating slot 28 formed therethrough and arranged in alignment with respect to the iilamentary cathode 25 aswell as the anode 426 and the cavity formed infthe'arc block 22. In addition, a thermionic emissive arc cathode'olsupportcd by `the removable end walll, is interposed between the flamentary cathode 25 and the collimating electrode 27, and arranged in alignment therewith'. B oth the anode 26 and the collimating electrode 27 are electrically connected to the source unit 20 which is in Vturn grounded; likewise, the tank 13 is grounded. A suitableA source of cathode bombardment voltage is adapted to'beconnected between the tilamentary cathode 25 andthe are cathode 67, the negative and positive terminals'of Vthe supply being connected respectively to the iil'arnentary cathode 25 and the arc cathode 67. Also, the arc cathode 67 and the cooperating anode 26 are adapted to be connected to a suitable source of are supply. It Should lbe noted that the above-described electrode a1'- ranger'nent is disclosed in the copending application of Louis F. Wouters, Serial No. 528,818, led March 31, i944. v Further, the removable end wall `18 carries ion accelerating lstructure 39 formedofcarbon or graphite and disposed in spaced-apart relation with respect to the wall of carries a lamentary the arc block 22 in which the slot 24 is formed. More specically, a slit 40 is formed in the ion accelerating structure 39 and arranged in substantial alignment with respect to the slot 24 formed in the wall of the arc block 22. A suitable source of accelerating electrode supply is adapted to be connected between the arc block 22 and the ion accelerating structure 39, the positive and negative terminals of the supply mentioned being respectively connected to the arc block 22 and to the ion accelerating structure 39. Further, the positive terminal of the ion accelerating potential is grounded.

The removable end wall 19 suitably supports a collector block 29 formed of stainless steel or the like and provided with two laterally spaced-apart cavities or pockets 30 and 31 which respectively communicate with aligned slots 32 and 33 formed in the wall of the collector block 29 disposed remote from the removable end wall 19. It is noted that the pockets 30 and 31 are adapted to receive two constituent isotopes of an element which have been separated in the calutron 10, as explained more fully hereinafter. Further, the inner wall 16 suitably supports a tubular liner 34 formed of copper or the like, rectangular in vertical cross-section, disposed within the tank 13 and spaced from the Walls 14, 15, 16 and 17. One end of the tubular liner 34' terminates adjacent the accelerating structure 39; and the other end of the tubular liner 34 terminates adjacent the collector block 29; the tubular liner 34 constituting an electrostatic shield for the high velocity ions traversing the curved paths between the slit 40 formed in the ion accelerating structure 39 and the slots 32 and 33 formed in the collector block 29, as explained more fully hereinafter. Finally, the tubular liner 34 is electrically connected to the ion accelerating structure 39 and to the collector block 29. Thus, it will be understood that the source unit and the tank 13 are connected to the positive grounded terminal of the accelerating electrode supply; while the ion accelerating structure 39, the tubular liner 34 and the collector block 29 are connected to the ungrounded negative terminal of the accelerating electrode supply; the ion accelerating structure 39, the tubular liner 34 and the collector block 29 being electrically insulated from the component parts of the tank 13.

Considering now the general principle of operation of the calutron 10, a charge comprising a compound of the element to be treated is placed in the charge receptacle 21, the compound of the element mentioned being one which may be readily vaporized. The end walls 18 and 19 are securely attached to the open ends of the tank 13, whereby the tank 13 is hermetically sealed. The various electrical connections are completed and operation of the vacuum pumping apparatus, not shown, associated with the tank 13 is initiated. When a pressure of the order of l05 to 10-4 mm. Hg. is established Within the tank 13, the electric circuits for the windings, not shown, associated with the pole pieces 11 and 12 are closed and adjusted, whereby a predetermined magnetic field is estab lished therebetween traversing the tank 13. The electric circuit for the heater 23 is closed, whereby the charge in the charge receptacle 21 is heated and vaporized. The vapor fills the charge receptacle 21 and is conducted into the communicating cavity formed in the arc block 22. The electric circuit for the larnentary cathode 25 is closed, whereby the lilamentary cathode is heated and rendered electron emissive. The electric circuit for the bombardment arc cathode 67 is closed, whereby the arc cathode is heated to electron emissive temperature by electron bombardment from the iilamentary cathode 2S. Then the electric circuit between the arc cathode 67 and the anode 26 is closed, whereby an arc discharge is struck therebetween, electrons proceeding from the arc cathode 67 through the collimating slot 28 formed in the collimating electrode 27 to theanode 26. The collimating slot 28 formed in the collimating electrode 27 defines the cross-section of the stream of electrons proceeding into therebetween.

the arc block 22, whereby the arc discharge has a ribbonlike configuration and breaks up the molecular form of the compound of the vapor to a considerable extent, producing positive ions of the element that is to be enriched with the selected one of its isotopes. A more detailed explanation of the operation of the aforesaid arrangement may be had by referring to the copending application of Louis F. Wouters, Serial No. 528,818, tiled March 31, 1944.

The electric circuits between the arc block 22 and the ion accelerating structure 39 are completed, the ion ac celerating structure 39 being at a high negative potential with respect to the arc block 22, whereby positive ions in the arc block 22 are attracted by the ion accelerating structure 39 and accelerated through the voltage impressed More particularly, the positive ions proceed from the cavity formed inthe arc block 22 through the slot 24 formed in the wall thereof, and across the space between the ion accelerating structure 39 and the adjacent wall of the arc block 22, and thence through the slit 40 vformed in the ion accelerating structure 39 into the interior of the tubular liner 34. The high-velocity positive ions form a vertical upstanding ribbon or beam proceeding from the cavity formed in the arc block 22 through the slot 24 and the aligned slits 40 into the tubular liner 34.

As previously noted, the collector block 29, as well as the tubular liner 34, is electrically connected to the ion accelerating structure 39, whereby there is an electricfield-free path for the high-velocity positive ions disposed between the ion accelerating structure 39 and the collector block 29 within the tubular liner 34. The high-velocity positive ions entering the adjacent end of the liner 34 are deflected from their normal straight-line path and from a vertical plane passing through the slot 24 and the aligned slit 40, due to the effect of the relatively strong magnetic tield maintained through the space within the tank 13 and the liner 34 through which the positive ions travel, whereby the positive ions describe arcs, the radii of which are proportional to the square roots of the masses of the ions and consequently of the isotopes of the element mentioned. Thus, ions of the relatively light isotope of the element describe an interior arc of relatively short radius and are focused through the slot 32 into the pocket 30 formed in the collector block 2D; whereas ions of the relatively heavy isotope of the element describe an exterior arc of relatively long radius and are focused through the slot 33 into the pocket 31 formed in the collector block 29. Accordingly, the relatively light ions are collected in the pocket 30 and are de-ionized to produce a deposit of the relatively light isotope of the element therein; while the relatively heavy ions are collected in the pocket 31 and are de-ionized to produce a deposit of the relatively heavy isotope of the element therein.

Of course, it will be understood that the various dimensions of the parts of the calutron 10, the various electrical potentials applied between the various electrical parts thereof, as well as the strength of the magnetic field between the pole pieces 11 and 12, are suitably correlated with respect to each other, depending upon the mass Vnumbers of the several isotopes of the element which is to be treated therein.

In the operation of the calutron 10, it is highly desirable that a relatively intense stable beam of positive ions be projected by the ion accelerating structure 39 through thc liner 34 toward the collector block 29 which operating condition requires that the source 'unit 20 presents to thc accelerating structure 39 a high density plasma surface which is extremely stable in shape, position and ion den sity. As has been heretofore described, in order to obtain such a plasma surface the rate of ion production by the -arc discharge in the source unit 20 must be substantially constant. This has been accomplished by controlling the heating energy applied to the arc cathode inversely as the arc current.

onsideringnowrthe electricalconnections ofthe ion generator of 4the. 'calutron 10, the busbars`64and c 'the'llanientary `cathode 25 y of the caluftron 410 and arvv connected to a suitable lament currentsupply 6 9,l ,the buslzvar 6 5 also being connected to the terminal-.O of lthe bombardment cathode voltage control network 72t V.The positive terminal Aof the arc current supply 77 is connected to the anode 26 yand the collimating ele'ctode 27 of the ion generatorvZt] and also to the grounded positiveztjerminal of the high voltage accelerating electrode supply, tlrenegative `terminal `of this latter supply being connected to'the accelerator structure '39'.of the 'calutron 10..' i The negative terminal `of the arc current supply 77.A is connected to the terminal D of the bombardment cathode voltage control network 72 and to the variable resistor 11( and terminal G ofV this network is connected to the positive terminal ofvthefcatho'de bombardment voltage supply/'74, this latter positive terminal being connected to the bom bardment'cathde 67 of the ion generator 2d. The nega'- tive terminal of the cathode bombardment voltage ysupply 74 is connected to the terminal B of the control network 72.

It will V'be observed that the cathode bombardment voltL age control network 72 functions'as a variable impedance responsive to the arc current llowing from the arc supply 77 to the arc between the bombardment cathode 67 and the anode 26 of the ion generator 20 for the purpose1 of controlling the bombardment current supplied from the cathode bombardment supply 74 so that a decrease in the arc current causes an incease in the bombardmentVv current between the'iilamentary cathode 25 and the bombardment cathode 67 and an increase in the arc currentcauses a `decrease in the bombardment current. This cathode bombardment current control network 72 consists of a pair of triodes 111 having the cathodes thereof connected together tothe center tap of the secondary of the transformer112 and to one terminal of the variable resistor 11.0 and to thefterminal D of the network.` The 'grids of thetriodes 111 are also connected together tothe other terminal of the variable resistor 110 and to the terminal G-v of the network. The anodes of the triodes 111 are connected to opposite terminals of the secondary of the transformer 112. The primary of the transformer 112 is connectedinseries with a source of alternating current supply, designated as A..C.,to the primary of the transformer 113. The terminals of the secondary ofthe transformer 113 are connected to the anodes ofthe full-wave rectifier 114 and thev center tap of this secondaryfis connected to kthe grid electrode l of the triode 117. The cathode of this triode 117 is connected to they grid of this triode through the resistor 116 and .this resistor is shunted byacondenser 115. The anode ofthe triode 1-17is con'- nected to the terminal` O of the network .and from this terminal-` to the busbar .65 supplying the tlame'ntary cathode 25 ofthe ion-generator 20. The cathode of the triode 1.17 and the centertap of the secondary winding of transformer. 113 supplying the cathode of the rectifier 114 are connected to the terminal B of the network 72, this terminal being connected to the negative terminal of the cathode bombardment voltage supply 74. c The physical connections of the embodiment of this invention shown in HFig. l having beeny described,. the operation `of this embodiment of this ion generator regulator `will now be described in detail. I t is noted that any reference to current flow hereinvpert'ains to electron current. Y Y c r It is assumed that the filament supply 69 is'fconnected to the lilament 25 as shown and the filament is heated to electron `emissive temperature so that .a copious supply of electrons are being emitted from this filamenti and are bombarding the bombardment cathode 67 so that this latter cathode is thereby heated lto .electron emissive temperature. Y This is accomplished by-the current -llow from the negative terminal ofthe cathode bombardment voltage supply 74 which it:` connected tothe, terminal B of the network 72 and through thief'terriiilal` to the cathode of the triode 117- and through Athis Qtrio'de'and .the terminal 4O of the network 72td`thebusbar 65 feeding `filament 25. Electron emis- 'sion"frornjhdlament 25k iiows to the bombardment cathode'f67 u'of the iongenerator under the stimulus of thepotential of `the cathode bombardment supply 74 andycurrent flowing ifrom, the bombardment cathode 65pz`r's'fses` `lthr`ough the busbar connected thereto to the positive terminal of the bombardment supply 74.v Current flowing from the arc current supply 77 passes from themeg i ney lterrnfirial thereof through the terminal D of the netwokn7l2, through the variable resistor 110 of thisnetwor'lc` to 'the terminal G` thereof to the bombardment cathdew'67 and fromthe bombardment cathode through' the ar"c`fchamber of the ion generator 20 to the auV def26thereof and `then lthrough the busbar connct'e'dlto` this Vanode to the psitiv'eterminal of the arc currentHsnpplyf/7. The arc current passing through the variable yresistor *11:0 `produces a potential drop acrosslthis Vresistor)which is applied between the` cathodes and'gd'relectrodes of thetriodes 111 so that the grid signal 'applied to these triodes 111 is varied in accordance qwitnmthe current through the resistor and the impedances of these triodes 111 are therefore correspondingly varied land the impedence of the transformer 1ll`2r`alsocontrolled;V As has been stated herein and asfis,'slic'nvrrin.` the drawings, the primary of the transformer 441 2 `is`"i1`1 series withV the primary of the transformer 113 'lsoutha't the primary 'potential applied to the transformer `113 may be controlled by the impedance of theitransform'er 112. The 'secondary of transformer 113 is connected to supply the grid potential to the trriode 117 so that the variation*l in the A. C. potential applie'dfto the. primary of the transformer V113 causes a corresponding change in the grid potential applied to the' of the tubi'1'17 thereby modifying the impeda Y of this tube and controlling therbomba'rdx'nent current' passingl from the filament 25 to the bombardment cathode 67off the ion generator. In other words, increasing theA arecurrent supplied by the arc current supply 77 reas'es the potential drop across the resistor 110 thereby increasingV the positive potential applied to the grids of the triodes 111 and reducing vthe impedance of these tubes causing a greater current to now through the secondary of the transformer 112. Thiscauses ya reduction yof the A. C. potential across the primary of this'tr'ansformer so that the potential applied "to vthe prini'ary of the transformer 113 is caused to increase with' the result that the negative grid bias applied to the triode 117 is increased and the bombardmentcurrnt passing: through this tube 117 to the bombaidme'nt cathode 67 is'decreased. This resultsin a reduction'of the electron emission from the bombardment"cath'od and a consequent reduction in arc current, opposing the original increase and tending to restore the arc current to its normal value. This' operation of the'ion generator is thereby regulated.

In Fig.' 3 is illustrateda modified form of the arc regulator in accordance with this invention and in this case the ion generator filament 25 is also connected to the ilament supply busbars 64 and 65 and the busbar 65 is connected to the terminal lO of the bombardment voltage control network 72a which corresponds to the network 72 of-Fig; l. The arc current supply 77 is connected with its positive terminal to the ion generator anode 26 and with its negative terminal to the bombardment cathode 67 of the ion generator through the terminals Da and Ga of the bombardment control network 72a. The terminals Ga and Da of the network 72a arep'conn'ected to the winding 81 associated with the-tetro'de 82 so that 'thiswinding is in effect conthe current'through the winding may be varied.

The positive terminal of the cathode bombardment supply 74 is connected to the bombardment -cathode 67 and the negative terminal of this supply 74 is connected to the terminal B of the network 72a and through this terminal to the cathodes of the trodes 100 and 101. The anodes of these tubes 100 and 101 are connected to the terminals of the inductance 102. The center tap of the inductance 102 is connected to the terminal O of the network 72a which is connected to the filament busbar 65.

The network 72a is provided with a pair of power supplies including the rectifier tubes 84 and 95 which are connected as full-wave rectifiers to rectify the outputs of the secondary windings of transformers 84a and 85a, respectively, connected to the anodes of these rectifiers. The output of rectifier 84 is filtered by the lter 83 and the output of this filter is connected across the voltage divider resistors 86 and across the potentiometer 91. Both these voltage dividers, resistors 86 and the potentiometer 91, are shunted by a voltage regulating gas discharge tube 87. A variable tap on the voltage divided 86 is connected to the control grid of the tetrode 82 and taps on this voltage divider are connected to the screen grid and the anode of the tube 82 through the resistors 88 and 89, respectively. The control grid of the tetrode 90 is connected to the anode of the tetrode 82 and the cathode of this tetrode 90 is connected to the variable contacter of the potentiometer 91 and also to the negative output terminal of the rectifier 95. The output of the filter of the rectifier 95 is connected across the voltage divider resistor 96 and a tap on this voltage divider network is connected to the screen grid of the tetrode 90 through the resistor 90a. The positive output terminal of the rectifier 95 is connected through the resistor 92 to the anode of the tetrode 90 and to the common connection of the resistors 103 and 104. The resistor 103 is connected to the grid of the tube 100 and to a terminal of the condenser 105, the other terminal of this condenser being connected to the cathode of this tube. The resistor 104 is connected to the grid of tube 101 and to a terminal of the condenser 106, the other terminal of this condenser being connected to the cathode of tube 101.

A pair of condensers 107 and 108 shunted by resistors 107a and 108s, respectively, are connected in series across the terminals OB of the control network 72a. Furthermore, a disabling switch consisting of switches 81a and 107b insulated from each other but ganged mechanically to be operable as a unit is provided for the purpose of by-passng the control network 72a, if desired, and for this purpose the switch 81a is connected across the terminals Ga and Da and the switch 107b is connected across the terminals O and B so that closing the switches 81a and 107b by-passes the apparatus 72a and the arc current instead of .dowing to the resistor 80 and winding 81, which is magnetically coupled to the tube 82, flows through the switch 81a, and the cathode bombardment 'current instead of owing through the tubes 100 and 101 and associated circuits, flows through the switch 107b.

Having traced through the physical connections of the wiring diagram illustrated in Fig. 3 the operation of the ion generator arc control shown and disclosed therein will be discussed.

As has been pointed out above the arc current of the ion generator 20 flows through resistor 80 and the inductive winding 81 when the switch 81a is open and the current flowing through the winding 81 sets up a magnetic field through this winding and through the tetrode 82 thereby affecting the impedance of the tube 82. The winding 81 is arranged so that the increased magnetic field thereof when the current owing therethrough increases causes the impedance of thetetrode 82 to increase with the result that the current thrvough the tetrode 90 conrolled by the control grid thereof is increased and the impedauces of the triodes 100 and 101 are increased.

As-are'sult the cathode bombardment current flowing betweenv the filament 25 and the bombardment cathode ,67 of theion generator through the tubes 100 and 101 is-decreased. The electron emission of the bombardment cathode is thereby decreased and the arc current flowing between the arc anode 26 and the bombardment cathode 67 is also decreased, opposing the initial increase and thereby restoring the arc current to approximately its original value. In this way the arc current of the ion generator is stabilized around some predetermined value and this may be changed manually by changing the value of the variable resistor shunting the coil 81.

The resistors 107a and 108a shunted by the condensers 107 and 108, respectively, are connected across the terminalsO and B for the purpose of carrying the principal cathodel bombardment current so that this current does not all have to ow through the tubes and 101 and these tubes need only to carry the current required for regulation purposes, the condensers 107 and 108 functioning as filter condensers.

In Fig. 4 is shown a still further modified form of arc regulator and in this case the bombardment cathode control network 72b, of somewhat simplified form, is employed instead of the network 72a shown in Fig. 3. The network 72b consists of a tetrode 120 having a pair of grids, a cathode and an anode, the cathode 121 thereof being connected to the grid 122 and to the bombardment cathode 67 of the ion generator 20 of the calutron. Furthermore, the cathode 121 of the tube 120 is also connected to one of the terminals of the potentiometer 124, the other terminal of this potentiometer being connected to the negative terminal of the arc current supply 77. The variable contactor of the potentiometer 124 is connected to the negative terminal of the battery 126, the positive terminal of this battery being connected to the grid 123 of the tube 120. The anode 125 of this tube is connected to the positive terminal of the bombardment cathode current supply 74. The negative terminal of this current supply 74 is connected to the filament busbar 65 and through this busbar to the filament 25 of the ion generator 20.

The operation of the embodiment of this invention shown in Fig. 4 is as follows: The ion generator filament 25 is heated to electron emissive temperature by the current supplied from the source 69 and electron current from the bombardment cathode supply 74 flows from the negative terminal of this supply 74 to the filament 25 and thence by electron emission to the bombardment cathode 67, heating it by bombardment to electron emissive temperature. From the bombardment cathode 67 the current fiows through tube of the control network 72b to the positive terminal of the bombardment cathode supply 74. The arc current supplied by the source 77 flows from the negative terminal thereof through the resistor of the potentiometer 124 in the control network 72b to the bombardment cathode 67 and through the arc to the anode 26 to the positive terminal of supply 77. A potential drop proportional to the arc current is produced across the resistor 124 having a polarity with respect to the grid 123 in opposition to the battery 126. Thus an increase in arc current and in the potential drop across that portion of the resistor 124 between the cathode 121 and the variable contactor thereof functions to decrease the positive bias applied to the grid 123 with respect to the cathode 121 so that the impedance of the tube 120 is thereby increased resulting in a decrease of current to the bombardment cathode 67 from the supply 74 and a consequent decrease in arc current, opposing the original increase. This operation is automatic and functions toustabilize the operation of the ion generator around some desired value of arc current. This desired valueV may be manually controlled or varied by varying the variablecontactor of the potentiometer 124 so that different amounts of the potential drop across the resistor of this potentiometer are used to control the impedance of the tube "120. v

While there has been described what is at present considered to be the two preferred embodiments of the in vetion, 'it will be further understood that various modifications may be made therein, and it is intended to cover in the appended claims -all such modifications as fall Withinv the true spirit and scope of the invention.

What is claimed is:

l. A- regulator for an ion generator comprising in combination an iongenerator having a thermionic emissive cathode and an anode, a source of current supply connected between said cathode and said anode for producing an' arc discharge therebetween, means for feeding material-to be ionized to` said arc discharge, and means responsive to the arc current between said cathode and said anode -for controlling the thermionic emission of said cathode.

2.The regulator for an ion generator comprising in combination an ion generator having a thermionic emissive cathodeand an anode, a source of current supply connected between said cathode and said anode for producing an arc discharge therebetween, means for feeding material tobe ionized to said arc discharge, and means including a thermionic device responsive to the arc current between said cathode and said anode for controlling the thermionic emission of said cathode.

3. -The regulator for an ion generator comprising in combination anion generator having a thermionic emissivecathode and an anode, a source of current supply connected between said cathode andv said anode for produing an arc discharge therebetween, means for feeding material to be ionized to said arc` discharge, andmeans including a variable impedance device responsive to the arc current between said cathode and said anode for controlling the thermionic emission of said cathode.

4. A regulator for an ion generator comprising in combination an ion generator having an electronemissive cathodefa bombardment cathode and an anode, a source ofcurrent-supply'connected between said electron emissive cathode and said bombardment cathode whereby electrons emitted by said electron emissive cathode bombard said bombardment cathode to raise thelatter to electron emissive temperature, a source of arc current supply connected between said bombardment cathode and said anode, means for feeding a substance to be -ionized between said bombardment cathode and said anode, and means responsive to the arc current between 'said bombardment cathode and said anode for controlling the current between 4said electronA emissive-cathode and -said bombardment cathode.

5. A regulator for an ion-generator comprising `in combination an ion generator having-an electron emissive cathode,'a,bombardment cathode-and an anode, a source of current supply connectedbetween said electron emis- Y sive' cathode and ysaid-bombardmentcathode whereby electrons emitted by said electron emissive cathode bombard said bombardment cathode to raise thelatter to electron emissive temperature, a source of arc current supply connected between said bombardment cathode and saidanode, meansffor feeding a substance to be ionized between said bombardment cathode and said anode, and

means including a thermionic device responsive to the arc current between said bombardment c'athode and said anode for controlling the current b'etweensaid electron emissive cathode and saidV bombardment cathode.

6. A regulator for an ion generator comprising in combination'an =ion` -generator having an'electron emissive cathode, a b'oinbar'dment`A cathode and an anode, a source of current supply connected between said electron'emissive cathode and said bombardment cathode 4whereby electrons emitted by said electron emissive cathoderbom- .bard said bombardment cathode to raise thev latter-to 'electron emissive temperature, a source of arc current 'is'u'p'ply connected betwensaid bombardment cathode and ,and said anode for controlling the current" between said electron emissive cathode and said bombardment cathode.

7. A regulator for an ion generator comprising in combination an ion generator having an electron emissive cathode, a bombardment cathode and an anode, a source of bombardment current supply connected between said electron emissive cathode and said bombardment cathode, a three electrode thermionic device having a cathode, a grid and an anode and being connectedin series with said source of bombardment current supply, a source "of arc current supply connected between said bombardment cathode and said anode, a second three electrode thermionic device having a cathode, a grid and van anode,'and a resistor connected in series with said arc currentsupply, said resistor being connected across the input of 'said second three electrode thermionic device, andmeans Vconnected between said last-mentioned thermionic devicefand said first-mentioned thermionic device for controlling the impedance of said hist-mentioned thermionic device in accordance with the arc current of said ion generator.

8. A regulator for an ion generator comprising in c'ombination an ion generator having an electron emissive cathode, a bombardment cathode and an anode, a source of bombardment current supply connected between said electron emissive cathode and said bombardment cathode, a three electrode thermionic device having a cathode, a grid and an anode and being connected in series with said source of bombardment current supply, a sourceof arc current supply connected between said bombardment cathode and saidanode, and means connected to said thermionic device for controlling the bombardment current in accordance with the arc current.

9. regulator for an ion generator comprising in combination an ion generator having an electron emissive cathode, a bombardment cathode and an anode, a source of current supply connected between said electron emissive cathode and said bombardment cathode, thermionic means connected in series with said source of bombardment cathode current supply, a source of arc current supply connected between said bombardment cathode and said anode, an electromagnetic winding connected in series with said arc current supply, a thermionic device associated with said electromagnetic winding, the impedance of said thermionic device being controlled by said electromagnetic: winding, and means connected between said thermionic device and said` thermionic means whereby the impedance ofv said thermionic device controls the impedance of said thermionic means to maintain the arc current of said ion generator substantially constant.

10. A regulator for an ion generator comprising in combination an ion generator having an electron emis siv'e cathode, a bombardment cathode and an anode, a source of current supply connected between said electron emissivecathode and said bombardment cathode, a thermionic impedance device connected in series with said bombardment cathode current` supply, said thermionic impedance device having a grid electrode associated therewith for controlling the impedance thereof, a resistor connected in series with said arc current supply, said resistor having connections for applying the potential drop across at least a portion thereof to the aforesaidl grid electrode of said thermionic impedance device whereby said thermionic impedance device functions to control the current to said bombardment cathode to maintain the arc current of said ion generator substantially constant.

ll. In a calutron having an ion source including a filament, a bombardment cathode, and an anode and suitable sources of current and voltageconnected ,thereto,l tne combination comprising an electrical signalgenerating desource, voltage controlling means connected to said signal generating means and adapted to receive signal voltage therefrom, and current regulating means connected between one of said sources of voltage and said bombardment cathode, said current regulating means being also connected to said voltage controlling means so as to receive signal voltage therefrom whereby said current regulating means acts to eliminate substantially all variations in current iiow through said ion source.

12. A calutron comprising an ion source including a filament, a bombardment cathode, and an anode, suitable sources of voltage and current connected to said ion source for establishing electron flow between said filament and said bombardment cathode and for establishing an are discharge between said bombardment cathode and said anode, heating means for maintaining said ion source at a desired elevated temperature, a reservoir adapted to contain an ionizable material, means for feeding said material into said arc discharge, current sampling means connected to said ion source for sampling the are discharge, current sampling means connected to said ion source for sampling the are discharge current in said ion source and producing a signal voltage proportional to variations therein, amplifying means connected to said current sampling means for increasing the magnitude of the signal voltage received therefrom, and variable impedance means connected between one of said voltage vsources and said ion source whereby variations in impedance of said variable impedance produce variations in said electron fiow between said filament and said bombardment cathode, said variable impedance means being also connected to said amplifying means for receiving signal voltage therefrom whereby electron ow between said filament and said bombardment cathode is varied inversely to the signal voltage obtained from said current sainpling means.

13. A calutron comprising an ion source having a filament, a bombardment cathode, and an anode, suitable sources of voltage and current connected to said ion source for establishing electron flow between said filament and said bombardment cathode and for establishing an are discharge between said bombardment cathode and said anode, heating means for maintaining said ion source at a desired elevated temperature, a reservoir adapted to contain an ionizable material, means for feeding said material into said arc discharge, current sarnpling means connected to said ion source for sampling said arc discharge current and producing a signal voltage in response thereto, a first variable impedance means connected to said current sampling means, and a second variable impedance device connected between one of said sources of voltage and said ion source whereby variations in the impedance of said second impedance device produce variations in the electron iiow between said filament and said bombardment cathode, said second impedance device being also connected to said first impedance device and receiving signal voltage therefrom whereby variations in said are discharge current are counteracted by said second impedance device so as to maintain said are discharge current substantially constant.

14. A calutron comprising an ion source having a filament, a bombardment cathode, and an anode, suitable sources of voltage and current connected to said ion source for establishing electron fiow between said filament and said bombardment cathode and for establishing an arc discharge between said bombardment cathode and said anode, heating means for maintaining said ion source at a desired elevated temperature, a reservoir adapted to contain ionizable material, means for feeding said material into said arc discharge, current sampling means connected to said ion source so as to produce a signal voltage proportional to variations in said are discharge current, amplifying means having an input and an output and at least one stage of amplification therebetween, said -input being connected to said current sampling means for receiving signal voltage therefrom, a first variable im- 12 pedance device of the saturable reactor type having at least two windings, one of said windings being connected to said output of said amplifying means, and a second variable impedance device connected between one of said sources of voltage and said ion source, and one of said windings of said first variable impedance device being connected to said second variable impedance device whereby variations in said electron flow proportional to said variations in said arc discharge current are produced.

15. In a calutron having an ion source which includes a filament, a bombardment cathode, and an anode, suitable sources of voltage and current connected to said ion source for establishing an arc discharge between said anode and said bombardment cathode and for establishing electron ow between said bombardment cathode and said filament, heating means for maintaining said ion source at a desired elevated temperature during operation of said calutron, a reservoir adapted to contain an ionizable material, and means for feeding said material into said are discharge, the combination comprising current sampling means having an electromagnetic winding connected in series with said arc current supply, a first variable thermionic impedance associated with said electromagnetic winding, amplifying means having an input and an output with at least one stage of amplification therebetween, said input being connected to said first variable impedance for receiving signal voltage therefrom, and a second variable thermionic impedance connected between one of said sources of voltage and said ion source, the impedance of said second variable impedance being connected to the output of said amplifying means and being controlled thereby, said variations in impedance of said second variable impedance serving to control the electron fiow between said filament and said bombardment cathode whereby said arc discharge current is maintained substantially constant.

16. In a calutron having an ion source which includes a filament, a bombardment cathode, and an anode, a source of voltage and current connected to said filament and to said bombardment cathode for establishing electron iiow therebetween, a second source of voltage and current connected to said bombardment cathode and to said anode for establishing an arc discharge therebetween, heating means for maintaining said ion source at a desired elevated temperature during calutron operation, a reservoir adapted to contain an ionizable material, means for feeding said material into said arc discharge, a current sampling device having an electromagnetic winding shunted by a variable resistor and a variable thermionie impedance, said winding being connected in series with said arc current supply and said ion source, a first vacuum tube having at least a cathode, an anode and a control grid, said control grid being connected to said variable impedance, a pair of triode vacuum tubes each having a cathode, an anode and a control grid, said control grids being connected to the anode of said first vacuum tube, and a tapped inductor having its outer ends connected t0 the anodes of said second pair of triode vacuum tubes, said indicator being also connected to the filament of said ion source and the cathodes of said triodes being connected to said bombardment cathode voltage supply whereby variations in said arc discharge current produce variations in the electron ow between said filament and said bombardment cathode, said last named variations serving to counteract the variations in arc discharge current.

References Cited in the file of this patent UNITED STATES PATENTS 1,419,547 Ehret June 13, 1922 1,628,678 Morrison May 17, 1927 1,683,194 Kearsley Sept. 4, 1928 2,149,080 Wolff Feb. 28, 1939 2,180,815 Meier Nov. 21, 1939 2,373,151 Taylor Apr. 10, 1945 

14. A CALUTRON COMPRISING AN ION SOURCE HAVING A FILAMENT, A BOMBARDMENT CATHODE, AND AN ANODE, SUITABLE SOURCES OF VOLTAGE AND CURRENT CONNECTED TO SAID ION SOURCE FOR ESTABLISHING ELECTRON FLOW BETWEEN SAID FILAMENT AND SAID BOMBARDMENT CATHODE AND FOR ESTABLISHING AN ARC DISCHARGE BETWEEN SAID BOMBARDMENT CATHODE AND SAID ANODE, HEATING MEANS FOR MAINTAINING SAID ION SOURCE AT A DESIRED ELEVATED TEMPERATURE, A RESERVOIR ADAPTED TO CONTAIN IONIZABLE MATERIAL, MEANS FOR FEEDING SAID MATERIAL INTO SAID ARC DISCHARGE, CURRENT SAMPLING MEANS CONNECTED TO SAID ION SOURCE SO AS TO PRODUCE A SIGNAL VOLTAGE PROPORTIONAL TO VARIATIONS IN SAID ARC DISCHARGE CURRENT, AMPLIFYING MEANS HAVING AN INPUT AND AN OUTPUT AND AT LEAST ONE STAGE OF AMPLIFICATION THEREBETWEEN, SAID INPUT BEING CONNECTED TO SAID CURRENT SAMPLING MEANS FOR RECEIVING SIGNAL VOLTAGE THEREFROM, A FIRST VARIABLE IMPEDANCE DEVICE OF THE SATURABLE REACTOR TYPE HAVING AT LEAST TWO WINDINGS, ONE OF SAID WINDINGS BEING CONNECTED TO SAID OUTPUT OF SAID AMPLIFYING MEANS, AND A SECOND VARIABLE IMPEDANCE DEVICE CONNECTED BETWEEN ONE OF SAID SOURCES OF VOLTAGE AND SAID ION SOURCE, AND ONE OF SAID WINDINGS OF SAID FIRST VARIABLE IMPEDANCE DEVICE BEING CONNECTED TO SAID SECOND VARIABLE IMPEDANCE DEVICE WHEREBY VARIATIONS IN SAID ELECTRON FLOW PROPORTIONAL TO SAID VARIATIONS IN SAID ARC DISCHARGE CURRENT ARE PRODUCED. 